Does anyone use any type of gun spray cleaners to hose out the internal parts on their M&P's? I've always used Brake Cleaner to hose out internals on metal guns and never had a problem. What would it do to the frame on a M&P?
Why do you do that? Do you drop the guns in puddles, mud or sand quite often?
It is really not necessary to hose down the inside of the frame unless you have done so, or unless you have fired 20,000 rounds without cleaning and you are gunked up a bit. Short of that, you just don't need to do it.
If you really need to clean out the frame, what is wrong with the traditional method - complete disassembly and wash off each part, then re-lube and re-assemble.
Also, remember that the M&P and the SIGMA, the SW Series and the SD Series all have the little felt pad to "modulate spring vibrations" in the trigger return spring. When that gets wet, it has known to disintegrate and without it, the trigger spring will "shatter." The material from which it is made "may" have changed over the years (that is pure speculation, and I am giving S&W some benefit of the doubt here as they were aware of the problem as one of their people was present when this happened, twice in one test,* after the SIGMA came out), but it still looks absorbent. If it is, remember, even if it does not "disintegrate," it will hold moisture or water and will surely cause the trigger spring to rust and then break. They recommend that LE Agencies change out that spring quite often, and that may be part of the reason why, although that is not the exclusive reason.
While I believe there is no danger in submerging or thoroughly wetting the inside of a Glock, Beretta or 1911 frame with anything, I am always very cautious about getting that felt pad wet on the M&P.
There have been discussions about it on this forum, and it is surprising how many people do not even know it is there. Remove the slide and pull the trigger to the rear. When the return spring "stretches," you will get a very clear view of the "tampon," as many have nicknamed it.
*If I recall correctly, they were "dunking" the SIGMA into water to cool it during a rapid fire portion of a gun magazine type of "endurance test." The disintegration of the felt pad occurred twice causing the trigger spring to break twice, with surprisingly few rounds fired. They attributed the spring breaking to the fact that the little pad (tampon) was soaked during the dunking. At least one person from S&W was present when this happened, and his name was mentioned in the article.